Improvement on Determination of Sulfide in Waste Water by Iodometry

Optimization for the conditions described in the standard method of iodometric determination of sulfides in waste water (HJ/T 60-2000) was made scrutinously, and the following modifications were given:① temperature of the water bath chosen:65℃; ② flow-rate and time of the 3 N₂-blowings:80 mL·min^-1 and 20 min for the 1st blowing, 300 mL·min^-1 and 10 min for the 2nd blowing and 400 mL·min^-1 and 6 min for the 3rd blowing; ③ 1 mol·L^-1 zinc acetate solution was selected as absorbent, and 3 mL of the solution were used to absorb H₂S liberated from the sample solution containing ≤1.5 mg·L^-1 of sulfides; ④ the modified method was proved to be valid for samples containing sulfides in the range of 0.4-3 mg·L^-1 and the portion of sample used for the determination should contain sulfides ≤1.5 mg·L^-1. On the base of waste water samples as matrixes, test for recovery of the proposed method was made by standard addition method, results of recovery found were in the range from 94.4% to 94.9%, with values of RSDs (n=6) ranged from 2.3% to 3.4%.